Holocene earthquakes on the Zemuhe Fault in Southwestern China

H. He, J. Ren


The Zemuhe Fault is a prominent active fault in Southwestern China. Seven ravines along a 5 km long fault scarp
indicate seven large magnitude earthquakes in the Holocene. The youngest four ravines were abandoned during
four large magnitude earthquakes, the age of which are constrained by radiocarbon data: ravines 7, 6, and 4 formed
in association with the earthquakes at A.D. 1850 and A.D. 814, B.C. 4477 ± 240 or older, and ravine 5 to a
paleo-event between B.C. 4477 ± 240 and A.D. 814. Three trenches excavated by earlier workers together with
a trench excavated and analyzed here revealed 3 or 4 earthquakes, which are consistent with those indicated by
the youngest five ravines. These radiocarbon-dated earthquakes mainly occurred within two temporal clusters:
the older cluster of two paleoearthquakes occurred approximately between B.C. 4250 and B.C. 6000, and the
younger cluster includes two historical earthquakes of the A.D. 814 and A.D. 1850. Each cluster lasted about
1000-2000 years. A tranquil period of about 5000 years separates the two clusters, during which only one large
magnitude earthquake occurred. Moreover, the average recurrence interval of large magnitude earthquake in the Holocene
is about 1400-1700 years. Comparison of the maximum horizontal displacement of the A.D. 1850 earthquake,
and the 85 ± 5 m cumulative lateral offset over the last 13-15 ka gives the average recurrence interval of
1000-1360 years. The different estimates may arise because moderate and small earthquakes produced a quite
high cumulative lateral displacement along the Zemuhe Fault during the Holocene.


Holocene earthquakes;Zemuhe Fault;Southwestern China

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DOI: https://doi.org/10.4401/ag-3444
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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X